1. Make the dough: mix the tepid milk, yeast, flour, sugar, salt, egg, and butter until smooth and elastic. This is a wet dough; you can reduce the milk a little if it is difficult to work with. Leave it in a warm place for about 30 minutes, or chill it for a few hours, which makes it much easier to work with.

2. Make the marzipan cinnamon filling: mix the marzipan, brown sugar, butter, cinnamon, and cornflour together to a paste.

3. Make the apple filling: cook the diced apple, sugar, cornstarch, cinnamon, and water together over medium heat for a few minutes until the apple softens. Transfer to a bowl and let it cool completely.

4. Make the pastry cream (original, untested): heat the milk until steaming. Whisk the egg yolks, sugar, and cornflour in a bowl, then slowly whisk in the hot milk. Return to the pan and cook over medium heat, whisking constantly, until thick and bubbling. Whisk in the vanilla, cover the surface with cling film, and cool completely.

5. Shape the ring (original, untested): grease a Bundt pan well (the original used 20 cm across the bottom and 25 cm across the top). Roll the dough on a floured surface into a large rectangle about 3 to 4 mm thick. Spread with the marzipan cinnamon paste, scatter over the cooled apple filling, and dot with about half the pastry cream. Roll up from a long side, cut the log in half lengthwise, twist the two halves together, and place the twist in the Bundt pan as a ring. Cover and let it rise in a warm place for about 30 to 45 minutes.

6. Bake at 180 C (conventional oven) for 35 to 40 minutes, or until the internal temperature reaches 88 C.

7. While it bakes, make the vanilla syrup: stir the boiling water, sugar, and vanilla together until the sugar dissolves. Brush it over the ring as soon as it comes out of the oven.

8. Let the ring cool completely in the tin.

9. For the icing, mix the icing sugar with a small drop of milk until thick. Warm it for a few seconds in the microwave, then pipe it over the ring.